Electrophotographic photosensitive material

ABSTRACT

A photoconductive glassy alloy containing selenium, antimony and an electric property controlling substance is used in a photoconductive layer of a photosensitive member for electrophotography comprising mainly three layers such as a support layer, a photoconductive layer and an insulating layer, or mainly four layers such as a conductive layer, an insulating layer, a photoconductive layer and an insulating layer.

States Patent [191 Tanaka et al.

[ ELECTROPHOTOGRAPHIC PHOTOSENSITIVE MATERIAL [75] Inventors: Hiroshi Tanaka; Takashi Saito, both of Tokyo, Japan [73] Assignee: Canon Kabushiki Kaisha, Tokyo,

Japan [22] Filed: Nov. 12, 1973 [21] Appl. No.: 414,820

Related US. Application Data [63] Continuation of Ser. No. 256,198, May 23, 1972, abandoned, which is a continuation of Ser. No. 1,867, Jan. 9, 1970, abandoned.

[30] Foreign Application Priority Data Jan. 17, 1969 Japan 44-3262 [52] US. Cl. 96/15 [51] Int. Cl U G03g 5/04 [58] Field of Search 96/15, 1 R; 75/134 G [56] References Cited UNITED STATES PATENTS 2,745,327 4/1956 Mengali 96/15 [451 Feb. 18, 1975 3,427,157 2/1969 Cerlon et al. 96/l .5 3,490,903 1/1970 Meyers et al. 96/1 .5 3,524,745 8/1970 Cerlon et al.. 96/'l.5 3,769,010 10/1973 Hanada 96/15 Primary Examiner-Norman G. Torchin Assistant Examiner-John L. Goodrow Attorney, Agent, or Firm Fitzpatrick, Cella, Harper & Scinto [5 7] ABSTRACT 1 mainly three layers such as a supportlayer, a photoconductive layer and an insulating layer, or mainly four layers such as a conductive layer, an insulating layer, a photoconductive layer and an insulating layer.

3 Claims, N0 Drawings 1 ELECTROPHOTOGRAPHIC PHOTOSENSITIVE MATERIAL This is a continuation of application Ser. No. 256,198, filed May 23, 1972 which was a continuation of Ser. No. 1,867, filed Jan. 9, 1970, both of which are now abandoned.

This invention relates to an electrophotographic photosensitive member, and more particularly, to an electrophotographic photosensitive member mainly composed of support, photoconductive layer and insulating layer and capable of forming electrostatic image on the surface of the insulating layer.

Heretofore, as photoconductive substances for photosensitive member used in conventioinal electropho tographic process, there have been well known amorphous selenium in Xerox process and zinc oxide in Electrofax process. However, those photoconductive materials have various disadvantages to be solved, for example, when amorphous selenium is used as photosensitive member for a long time, the amorphous selenium is converted to a more stable metallic selenium, and thereby the physical properties are changed and the dark resistance and physical strength are lowered. As the result, the solenium can not be used any more and thus the life of the photosensitive member is substantially determined by the conversion of the amorphous state to metallic selenium state. In addition to such deterioration caused by crystallization of amorphous selenium, amorphous selenium is hardly sensitive to a long wave length region with respect to spectrum sensitivity and thereby the light source of imagewise exposure is restricted. Neither amorphous sele nium is suitable for reproduction of colored original image nor color-reproduction.

A photosensitive member having amorphous selenium as the photoconductive layer is usually made by depositing amorphous selenium on an electrically conductivesupport, and the photosensitive member thus produced is subjected to electrophotographic processes such as charging, exposure, developing and transferring and such processes are effected on the surface of the photoconductivelayer. Therefore, the surface of the photoconductive layer is damaged by various external factors such as effect of temperature, oxidation with air, abrasion, pressure and the like, and thereby the life of the photosensitive member is shortened and furthermore the damaged portion as mentioned above becomes crystal seed and accelerate crystallization of the amorphous selenium and thus the life of the photosensitive member is further shortened.

The present applicant has already developed various electrophotographic processes, for example, inventions disclosed in U.S. Ser. No. 563899 filed July 8, 1966 and U.S. Ser. No. 571538 filed Aug. 10, 1966. These electrophotographic processes comprise employing a photosensitive member having an insulating layer closely contacted with a photoconductive layer, and effecting three steps, that is, primary charging, expopsure simultaneously with secondary charging of a polarity opposite to that in the primary charging, or A.C. discharging, and whole surface exposure, to form electrostatic images of high contrast on the surface of insulating layer. The photosensitive member used in these processes is composed mainly of three layers. i.e. insulating layer, photoconductive layer, and conductive or insulating support, or composed mainly of four layers, i.e., insulating layer, photoconductive layer, insulating layer and conductive layer, and at least one layer adjacent to the photoconductive layer should be transparent to a radiation to which the photoconductive layer is sensitive. Unlike conventional Carlson process, in this photosensitive member electrostatic images are not formed directly on the photoconductive layer, but on the insulating layer, and various electrophotographic procedures such as developing, transferring, cleaning and the like are effected on the surface of the insulating layer. Therefore, the photoconductive layer is hardly damaged in this photosensitive member so that neither the crystallization of amorphous selenium occurs nor is accelerated. Therefore, the photosensitive member is hardly deteriorated and shows stable performance for a long time. In such photosensitive member having an insulating layer on a photoconductive layer does not have both charge retaining function and photoconductive function in the photoconductive layer, but the two functions are allotted to the insulating layer and the photoconductive layer and thereby the burden to the photosensitive layer is lightened. In other words, a highly sensitive material is generally of low electrical resistance and the charge retaining ability is low before imagewise exposure, but the process employing the above-mentioned photosensitive member can effectively utilize a highly sensitive material of low resistance which is not preferred in usual electrophotographic processes. As the result, according to such process, the photoconductive material can be selected from wide material sources without restricted by various electric characteristics.

This invention relates to a photosensitive member having an insulating layer on a photoconductive layer.

An object of this invention is to provide a photosensitive member of high sensitivity and exhibiting stably the function for a long time.

Another object of this invention is to provide a photosensitive member in which the sensitivity and the spectrum sensitivity region can be relatively easilycontrolled in accordance with the required photoconductive characteristics. a

A further object of this invention is to provide a photosensitive member having high resolving power and strong surface.

A further object of this invention is to provide a photosensitive member which is composed mainly of support, photoconductive layer and insulating layer in which the photoconductive layer of a photosensitive member containing an insulating layer on which surface electrostatic images are formed, is an alloy comprising at least selenium, antimony and electric property controlling substance and is in a glass state. The photoconductive layer of the photosensitive member of this invention contains an alloy comprising mainly selenium-antimony and additionally an electric property controlling substance.

The electric property controlling substance used in this invention is a substance which can impart a sensitizing effect to and widen the spectrum sensitivity region of the amorphous selenium-antimony system exhibiting stably the photoconductive property for a long time and can form a glassy alloy with the seleniumantimony system.

Representative examples of the: electric property controlling substance are Cu, Ag, Au, Zn, Cd, Hg, Ga, In, Tl, Ge, Si, Sn, Pb, Bi, S, Te and the like and oxides thereof. in practical use, more than one of them may be used in combination.

The change of electric property of the seleniumantimony system photoconductive material caused by adding such electric property controlling substance thereto is similar to that caused by adding a metallic sensitizer to an inorganic photoconductive material. That is, by adding the electric property controlling substance, the sensitivity and spectrum sensitivity region of the selenium-antimony system can be enhanced, but often the resistance in dark place is adversely lowered and this unfavorable effect impairs the electrostatic latent image retaining ability in electrophotographic processes. Therefore, if the photoconductive layer of this invention is applied to a conventional photosensitive member comprising a photoconductive layer laminated on a support, the construction of the photosensitive layer is often seriously limited due to lowering of charge retaining ability caused by the addition of the electric property controlling substance. That is, in a photosensitive member composed of a photoconductive layer laminated on a support, the photoconductive layer should have a resistance (at dark place) sufficient to process a charge retaining ability and the resistance is higher than about IO Q-Cm. Since the addition of an electric property controlling substance lowers the electric properties such as resistance in many cases, the addition of an electric property controlling substance to the photoconductive layer is substantially limited from practical point of view.

On the other hand, according to the present invention, the charge retaining ability is attributed to the insulating layer and the photoconductive layer is requested only to have an excellent photoconductivity and therefore, the limitations as mentioned above are not requested. And the electric property controlling substance can be optionally selected and prepared in accordance with the requested photoconductivity.

The amount of the electric property controlling substance to be added to the selenium-antimony alloy is fundamentally restricted by the two factors, one is that the resistivity of photoconductive layer is not lower than 1 X lOQ.cm and the other is that the photoconductive layer is glassy. In view of the two factors as above, the amount of the electric property controlling substance to be added is relatively small, but such small amount can effectively improve electric properties, mainly sensitivity. The thickness of photoconductive layer preferably ranges from to 300 t.

In the foregoing, the construction of photoconductive layer of photosensitive member according to this invention is described. It is not yet fully understood the reason why the photoconductive material comprising fundamentally selenium, antimony and electric property controlling substance shows high sensitivity and wide spectrum photosensitivity region. However, the photoconductive material used in electrophotography is amorphous, but it can be handled in a similar to photosemiconductor. Therefore, it is considered that the electric property controlling substance behaves as impurity for semiconductor with respect to the selenium-antimony material and makes a level corresponding to so-called impurity energy level and this is excited by a radiation energy of relatively long wave length such as, for example, 700 mu to form easily charge carriers and as the result, there is obtained a photoconductive material having high sensitivity and wide spectrum photosensitive region.

Another construction of photosensitive member according to this invention is described below. Firstly, the insulating layer in the photosensitive member of this invention is preferably of high resistance, capable of retaining electric charge, and of large abrasion resistance. Examples of the insulating layer are high polymer films such as film offluorine containing resin, polycarbonate resin, polyethylene resin, cellulose acetate resin, polyester resin and the like, or inorganic materi als such as glass ceramics of SiO;, Aigog and the like. When the exposure is effected through the insulating layer, the insulating layer should be transparent to a radiation to which the photosensitive layer is sensitive, but when the exposure is effected from a side opposite to the insulating layer with respect to the photoconductive layer, it is not necessarily transparent to the radiation, but opaque insulating layer may be also used. However, in the latter case the support should be transparent. Further, the thickness of insulating layer ranges preferably from 6 to 50 ,u.

As the-support used in this invention, there may be mentioned, for example, a conductive support, insulating support or a support comprising a conductive layer laminated with an insulating layer. Further, when an insulating support is used, electrostatic images can be formed on both sides of the photosensitive member and it is preferable to employ a double corona discharging system capable of charging the photosensitive member from both sides. Furthermore, when a support composed of an insulating layer laminated with a conduc tive layer is used, the photosensitive member is fundamentally composed of four layers, that is, an insulating layer, a photoconductive layer, an insulating layer and a conductive layer.

As conductive support used in this invention, any supporting material having conductivity may be selected from wide sources. For example, there may be mentioned metallic conductive material such as tin, copper, aluminum and the like and a hygroscopic paper and an aluminum laminated paper.

As insulating support, any supporting material may be used regardless inorganic and organic natures as far as the material is of insulating property. It is not necessary that the insulating support satisfies the conditions as requested for the insulating layer as mentioned above. Naturally the insulating support may be the same material as that of the insulating layer.

When the insulating support is used in a photosensitive member which is used in such a process that the exposure is effected from the support side, it is necessary that the insulating support is transparent to a radiation to which the photoconductive layer is sensitive. Furthermore, the above mentioned materials may be used for a support consisting of an insulating layer laminated with a conductive layer. When transparency is requested, there may be used transparent conductive material such as Nesa glass, polyvinylcarbazole and the like.

in the following, there are illustrated procedures for producing photosensitive members having a photoconductive layer of glassy alloy comprising selenium, antimony and electric property controlling material. The following examples are given for illustration, but by no means for limitation of this invention.

EXAMPLE 1 A mixture of Se of high purity (99.99%), 72 parts by weight, Sb parts by weight, and Te 8 parts is sealed in a vacuum quartz tube, heated and melted at 500C for about 6 hours to form a uniform dispersion system. The resulting melted product is poured into a distilled water to form powder solid matter followed by drying sufficiently. By a vacuum depositing method, the alloy thus obtained is deposited on an aluminum base plate maintained at 60 to 80C to form a glassy thin film, and thus a photoconductive layer of about 60 y. thick is obtained. Then, a polyester film of p. thick is ad hered to the photoconductive layer with epoxy resin to produce a highly sensitive photosensitive plate.

EXAMPLE 2 The procedure of Example 1 is repeated by using a mixture of Se 85 parts by weight, Sb 10 parts by weight and Ge 5 parts by weight in phase of Se, Sb and Te to 20 light of about 10 lu x to form latent images having electrostatic contrast of about 1,000V.

An example of another method is that the secondary corona discharging as mentioned above is effected by A.C. corona discharging. An electrostatic contrast of about 600V is obtained by applying a primary corona discharging of7l(V and a secondary A.C. corona discharging of 5.8KV.

In the former process, a particularly high contrast is obtained, and in the latter process, reproducibility of half tone is excellent.

There are, for example, further processes applicable to the photosensitive member of this invention as shown in the following table. For example, Process A refers to an electrophotographic process comprising the steps, positive primary charging, negative secon dary charging direct exposure, development and radiation (recovering the decay of photosensitive member by irradiating infrared ray etc.), and Process G refers to an electrophotographic process comprising the steps, positive primary charging, A.C. discharging simultaneously with exposure, whole surface irradiation, developing and irradiation.

Primary Secondary A.C. Simultaneous Direct Whole surface Process charging charging discharging exposure exposure irradiation Development Irradiation A 0 0 O B 0 0 0 C 0 0 0 0 D 0 0 0 0 E 0 0 0 0 F 0 0 0 0 G 0 0 O 0 (J H 0 O 0' O 0 with ethyl cellosolve is applied thereto by a flowingdown coating method to form a surface insulating layer of about 10 1. thick.

The photosensitive plates produced as above are used for forming electrostatic images as follows. The 40 polarity of voltage to be applied is selected appropriately in accordance with the type of photoconductivity of the photosensitive plate, for example, when the photoconductive layer is preferably of N-type, the primary charging is positive while when it is of p-type, the primary charging is preferably negative. In the following, the electrostatic image forming procedure is explained, for example, by using a photosensitive plate containing a photoconductive layer of ternary alloy of Se-S- b-Te. The surface of insulating layer of the photosensitive plate is charged to about-2,000V with a corona discharging of 6KV, and exposed at about one lux.sec simultaneously charged by a secondary corona discharging of +6KV and then the whole surface of the photosensitive member is uniformly irradiated with a What is claimed is:

1. An electrophotographic photosensitive member comprising a support layer, a photoconductive layeroverlying the support layer and an insulating overlying the photoconductive layer and at least one of the layers adjacent to the photoconductive layer being transparerit to a radiation to which the photoconductive layer is sensitive, characterized in that the photoconductive layer comprises an amorphous glassy alloy containing about 72 by weight of selenium, about 10 20% by weight of antimony and about 5% by weight of germanium and has a resistivity at dark place of not less than 1X10 ohm-cm.

2. An electrophotographic photosensitive member according to claim 1 wherein the support layer is characterized by having insulating properties.

3. An electrophotographic photosensitive member according to claim ll wherein the support layer is characterized by being electroconductive. 

1. AN ELECTROPHOTOHRAPHIC PHOTOSENITIVE MEMBER COMPRISING A SUPPORT LAYER, A PHOTOCONDUCTIVE LAYER OVERLYING THE SUPPORT LAYER AND AN INSULATING OVERLYING THE PHOTOCONLAYER AND AT LEAST ONE OF THE LAYERS ADJACENT TO THE PHOTOCONDUCTIVE LAYER BEING TRANSPARENT TO A RADIATION TO WHICH THE PHOTOCONDUCTIVE LAYER IS SENSITIVE, CHARACTERIZED IN THAT THE PHOTOCONDUCTIVE LAYER COMPRISES AN AMORPHORUS GLASSY ALLOY CONTAINING ABOUT 72 - 85% BY WEIGHT OF SELENIUM, ABOUT 10 20% BY WEIGHT OF ANTIMONY AND ABOUT 5% BY WEIGHT OF GERMANIUM AND HAS A RESISTIVITY AT DARK PLACE OF NOT LESS THAN 1$1011 OHM-CM.
 2. An electrophotographic photosensitive member according to claim 1 wherein the support layer is characterized by having insulating properties.
 3. An electrophotographic photosensitive member according to claim 1 wherein the support layer is characterized by being electroconductive. 